Exotic palm weevils which may present a threat for southern countries
It may be recalled that Rhynchophorus ferrugineus (red palm weevil - Coleoptera: Curculionidae: Rhynchophorinae) has recently been introduced into Spain (see EPPO RS 96/096 and 97/010). It probably came in the 1990s on ornamental palms, damage was observed in 1993 and the presence of this species was reported in 1996. This was the first record of R. ferrugineus in Europe. This species originating in south-east Asia and Oceania, has also been introduced in the last decades into the Near East region. In Spain, serious damage has been observed on Phoenix canariensis. Presence of the weevil is still limited to the coastal area from Motril (Granada) to Nerja (Málaga) in Andalucía, and the pest is under eradication. Studies on possible control methods are being carried out in Spain, and Barraco et al. (1998) have found that fipronil can provide a good larval control in the laboratory. On the basis of laboratory, field observations and bibliography, Esteban-Durán et al. (1998) have reviewed the biological characteristics of various beetles of the Rhynchophorinae subfamily which could potentially become pests of palm trees in Spain and other countries of the European Union (more particularly southern countries). For each species, a brief description of adult, egg, larva and pupa is given, as well as a list of host plants and a geographical distribution. The authors concluded that considering host range, geographical distribution and potential harmfulness, the most threatening species are R. ferrugineus and R. palmatum. Other species like Dynamis borassi, R. quadrangulus and Matemasius cinnamominus were considered of little importance. R. phoenicis, R. vulneratus and R. bilineatus were considered of intermediate importance for Spain, but it is stressed they can cause very serious damage on their host palms, respectively in sub-Saharan Africa, Asia and Papua New Guinea. The authors felt that the current phytosanitary requirements for palm imports are not adequate to prevent possible introductions of such insect pests. The detection of living stages inside plants by visual inspection is very difficult. In addition, young plants can be infested by eggs or larvae which are difficult to see. The authors suggested that these insects could be effectively detected by using sound detectors on plants kept in quarantine.
Rhynchophorus ferrugineus
Host plants: Areca catechu, Arenga pinnata, Borassus flabellifer, Caryota maxima, C. cumingii, Cocos nucifera, Corypha gebanga, C. elata, Elaeis guineensis, Metroxylon sagu, Oreodoxa regia, Phoenix canariensis, P. dactylifera, P. sylvestris, Sabal umbraculifera, Washingtonia sp. etc. It can also attack Agave americana, Saccharum officinarum.
Geographical distribution
EPPO region: Egypt, Spain. Esteban-Durán et al. suggested that it is probably present in Algeria, Morocco and other countries in North Africa but this has not been confirmed by the official authorities.
Asia: Bangladesh, Cambodia, China, India, Indonesia, Irak, Iran, Japon, Laos, Malaysia, Myanmar, Pakistan, Philippines, Qatar, Saudia Arabia, Sri Lanka, Taiwan, Thailand, United Arab Emirates, Vietnam.
Africa: Egypt.
Oceania: Australia (doubtful), Papua New Guinea, Solomon Islands.
Rhynchophorus palmatum
Host range: Acrocomia aculeata, A. lasiophata, A. sclerocarpa, Attalea coheme, Bactris major, Chrysalidocarpus lustescens, Cocos nucifera, C. coronata, C. fusiformis, C. romanzofiana, C. schizophylla, C. vagans, Desmoncus major, Elaeis guineensis, Euterpe braodwayana, Guilielma spp., Manicaria saccifera, Maximiliana caribaea, Metroxylon, sagu, Oreodoxa oleracea, Phoenix spp., Sabal spp., Washingtonia spp. It can also attack Gynerium saccharoides, S. officinarum, Carica papaya, Jaracatia dodecaphylla, Ananas sativa, Musa spp. and Ricinus spp.
Geographical distribution:
North America: Mexico.
South America: Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Peru, Surinam, Uruguay, Venezuela.
Caribbean and Central America: Belize, Costa Rica, Cuba, Dominica, El Salvador, Grenada, Guadeloupe, Guatemala, Honduras, Martinique, Nicaragua, Panama, Puerto Rico, St Vincent,. Trinidad and Tobago.
Note: it must be stressed that R. palmatum is the vector of the nematode Rhadinaphelenchus cocophilus, causal agent of the red ring disease which has a very serious economic impact on cultivated palm trees in South and Central America.
Rhynchophorus phoenicis
Host plants: Borassus spp., Elaeis guineensis, Hyphaene spp., Phoenix spp. (including P. dactylifera).
Geographical distribution: tropical and equatorial Africa (from Senegal to Ethiopia, and to South Africa). The authors mentioned speculation about a possible introduction into South America.
Rhynchophorus vulneratus
Host plants: Areca catechu, Arenga saccharifera, Cocos nucifera, Corypha gebanga, Elaeis guineensis, Livistona chinensis, Metroxylon sagu, Oncosperma tigillaria, O. horrida, Oreodoxa regia.
Geographical distribution:
Asia: Indonesia (Borneo, Java, Sumatra and other islands), Japan (south), Malaysia, Philippines, Thailand.
Oceania: Papua New Guinea.
Rhynchophorus bilineatus
Host plants: Cocos nucifera, Metroxylon sagu, M. solomonense.
Geographical distribution:
Asia: Indonesia (Buru, Sulawesi, Maluku).
Oceania: Papua New Guinea, Solomon islands.
Sources
Esteban-Durán, J.; Yela, J.L.; Beitia-Crespo, F.; Jiménez-Alvarez, A. (1998) Curculiónidos exóticos susceptibles de ser introducidos en España y otros países de la Unión Europa a través de vegetales importados (Coleoptera: Curculionidae: Rhynchophorinae).
Boletín de Sanidad Vegetal, Plagas, 24(1), 23-40
Barranco, P.; de la Peña, J.; Martín, M.M.; Cabello, T. (1998) Eficacia del control químico de la nueva plaga de las palmeras Rhynchophorus ferrugineus (Olivier, 1790) (Col.: Curculionidae).
Boletín de Sanidad Vegetal, Plagas, 24(1), 23-40
CABI maps no. 258 ; 259.